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Pest Alerts for Vegetable Growers: Jun 11, 2015

June 11, 2015

Vegetable scouting sheets can be found on the UMass Extension Vegetable Program website. When not given here, refer to the New England Vegetable Management Guide for scouting thresholds and treatment options.

Allium: Onion thrips: Treat if thrips reach 1 per leaf. A field scouted in Hampshire Co., MA was well above threshold (3/leaf) in bare ground onions, but onions grown on adjacent black plastic were below threshold (0.25/leaf). Leek Moth chewing damage and one pupa were observed in a Chittenden Co. VT onion field. This pest has only been documented in NY and VT, but not yet in MA, NH, CT or RI.

Basil downy mildew has been reported in a New Jersey field, and last week on home gardener basil plants in CT and VA. Basil growers should scout this week and initiate a preventive fungicide program if the disease is reported anywhere in their state.

Brassica: Cabbage root maggot are pupating in Franklin Co., MA, but we also saw new eggs so newly planted crops may still be at risk (worth scouting).. In Washington Co., RI one broccoli and kale crop scouted was 12% affected by feeding damage on roots but no maggots were found. Diamondback Moth larvae and pupae were seen on cabbage but not broccoli in Washington Co., RI Imported cabbage worm is at threshold of one caterpillar per plant in Washington Co. RI.

Corn: European corn borer: Based on the accumulated growing degree days (Table), European Corn Borer (ECB) is laying eggs in all locations but Middletown, RI (egg laying begins at 450 GDD base 50F).  Egg hatch is expected at approximately 540 GDD and peak flight (631 GDD) is expected in the next week for some locations. Both the New York (EII) and Iowa (Z1) strains are now being captured from the locations reporting (Table 3). Scout emerging tassels for the presence of ECB larvae by inspecting the tassels of 50 to 100 plants, in groups of 5 to 20 plants, throughout the field. Treat if more than 15% of the plants have one or more larvae present.  If you have early corn in silk now, this corn will attract the most egg-laying, but treatment decisions should not be based on scouting. ECB will lay eggs near the ear and emerging larvae will bore directly into ears. Therefore, if you have silk now and GDDs indicate that ECB is laying eggs) or eggs are hatching, one or two insecticide applications at 5-7 day intervals can be effective for controlling ECB on this advanced corn.  Traps were recently put out in VT and RI and have not yet reported any moths. Corn Earworm: If you have corn coming into silk, it is time to put out Corn Earworm traps. Three traps in Erie, Yates and Monroe Cos. NY reported CEW captures with one capturing as many as 7 moths per trap.

Cucurbit: Striped cucumber beetle: Cucumber beetles were reported above threshold of 1 beetle per 2 plants in a field of summer squash in Washington Co., RI. In Hampshire Co., MA striped cucumber beetle is below threshold in a field but above threshold in a high tunnel in Hampshire Co. MA. Reports from NH indicate this pest is active there on very young pumpkin and squash just germinating. One Squash vine borer was captured in a trap in a summer squash field in Hampshire Co. MA but not in traps in RI or NH; time to put out Heliothis net traps with squash vine borer lures in summer squash, zucchini, or pumpkin fields to monitor this pest on your farm. Spray threshold of 5 moths per trap has been successful for both organic and conventional farms. Population pressures vary greatly from farm to farm, so it is important to trap in your own fields for this pest. Melon aphids were found heavily infesting high tunnel cucumbers with some mummified by wasp parasites in Washington Co., RI.

Solanaceous: Colorado potato beetle: Adults and eggs have been found in Franklin and Hampshire Cos., MA and Washington Co., RI at high pressure. Larvae must be active out there somewhere! Thresholds are (per plant, or stalk once plants reach 12”): 0.5 Adult, 4 small larvae, or 1.5 large larvae. Keep an eye out for CPB as they emerge! Three-lined potato beetle adults are active in Hampshire Co., MA, Chittenden Co.,VT and Washington Co., RI but pressure is low. Tomato hornworm adult moth and pupae were found in high tunnel tomatoes, which means that this pest is overwintering. This is an important pest for those growing tomatoes consecutively in tunnels. Scout tomatoes in tunnels and greenhouses now. Potato aphid (both pink and green) were found in hot spots on high tunnel tomato in Washington Co., RI and throughout the crop in greenhouse tomato in Roxbury, MA.

Multiple: Verticilium wilt in okra is affecting 100% of a crop in a field with a history of the disease in Franklin Co., MA.  Submit samples to a diagnostic lab if eggplant, tomato, pepper, potato or okra are exhibiting the symptomatic yellowing and wilting of lower leaves followed by V-shaped lesions which are widest at the leaf margin. Leaf miner eggs were scouted above threshold of 5% of plants with egg masses in Franklin Co., MA on Swiss chard indicating that this pest is still a potential threat in spinach, chard and beet greens. Milkweed is budding now in Washington Co., RI.  Now is the ideal time to cultivate or even mow this weed down if it is in your pasture or vegetable fields since the plant has expended most of its energy reserves to flower.